You are currently viewing Free Network Tools Part 1 – Nokia QoS MBS Calculator

Free Network Tools Part 1 – Nokia QoS MBS Calculator

Please feel free to use our Nokia QoS MBS calculator below to calculate the correct value to set the MBS. The MBS is the Maximum Buffer Size and controls how long packets can remain in the queue under congestion. This value can make a big difference to your network performance.

This page will make up part of our overall Nokia QoS Guide we are aiming to build up. We also can provide expert level consultancy for QoS or any other networking technology across many vendors. Please contact us for more information.

MBS Explanation

So what is the MBS? The Maximum Buffer Size is a portion of physical memory on the relevant line card that is allowed to be used for your queue depth. It is taken from the shared buffer space. All of your traffic will pass through here as it egresses/ingresses a queue – therefore, if the MBS = 0, no traffic can pass through.

I’ll explain the link between MBS and CBS in a separate post on CBS.

The MBS is essentially the biggest amount of data that can be held in your queue, the bigger the queue size and the slower the playout rate, the higher your latency will be.

The following image is a graphical representation of a single ingress or egress queue. NB – this doesn’t show the HPO portion – this will be explained in a separate article.

Nokia MBS and CBS Queue

The Nokia QoS MBS Calculator

The inputs to the calculator should be:

  • Service Rate – this is generally your PIR and should be the highest rate the queue will be serviced
  • Max Delay – this is the highest acceptable delay – note this will be different per queue and per traffic type – ie EF voice would require a very low max delay. This is also entered in seconds, so 50ms max delay would be entered as 0.05. Note, if your traffic is congested and held in the queue, and is not serviced at the expected rate as your queues are over-subscribed – then the latency experienced will be higher than calculated.

The above calculator is based on the formula defined by Ram Balakrishnan in his fantastic book – Advanced Qos For Multiservice Networks. This book is a few years old now, but qos principles still remain and the Nokia implementation of qos for both access and network has not changed massively.

Feel free to bookmark this page and come back as often as you like when prepping queue configurations.

If you do need assistance to configure your Nokia QoS or any other vendor QoS, please do reach out to us – we can have an initial chat and work out the requirements and provide you with an expert level consultancy. You can contact us using our form.

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